Re: Why context-free?

henry@spsystems.net (Henry Spencer)
29 Oct 2005 21:27:21 -0400

          From comp.compilers

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From: henry@spsystems.net (Henry Spencer)
Newsgroups: comp.compilers
Date: 29 Oct 2005 21:27:21 -0400
Organization: SP Systems, Toronto, Canada
References: 05-10-053 05-10-061 05-10-062
Keywords: design, parse

Our moderator writes:
>...As far as extending the syntax on the fly, that avenue was
>extensively investigated in the 1970s in languages like IMP-72 and
>EL/1, all of which died. We discovered that if you can write every
>program in a slightly different language, six months later you won't
>remember what each language was and you won't be able to read any of
>them...


In a recent interview, Alan Kay suggested that while extensibility
*is* useful, there should be "a fence to hop" to get into
extension-writing mode. His observation is that even the best
programmers tend to do a very bad job on extension design when they're
doing it as part of a programming project, because the desire to get
on with the project discourages the careful thought that makes good
extensions.


This fits with something I've observed in the past: building a library
and building a program are two different jobs, which often want to use
somewhat different sets of language features.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. | henry@spsystems.net


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